1. Field of the Invention
The present invention relates to compressors, and more particularly, to a reciprocating type compressor, in which a compression rate of refrigerant is reduced relatively, a re-expansion rate is increased, for maximizing a suction efficiency.
2. Description of Related Art
In general, the compressor receives a working fluid from an evaporative heat exchanger, compresses, and supplies the working fluid to a condensing heat exchanger. FIG. 1 illustrates a related art reciprocating type compressor that compresses a gas inside of a cylinder by means of reciprocating motion of a piston connected to a connecting rod, which will be described.
The reciprocating type compressor is provided with a case 10, an electric driving part 20, and a compression part 30. The case 10 has an upper shell 12 and a lower shell 11, joined together to enclose an inside space of the case 10. There is refrigerating machine oil held in a lower part of an inside of the lower shell 11 to an appropriate depth for preventing wear of various machine components. The electric driving part 20 has a stator 21 for receiving a current to generate an electro-magnetic force, and a rotor 22 for generating a rotating force by the electro-magnetic force from the stator 21.
The compression part 30, compressing the working fluid by the rotating force from the electric driving part 20, has a crank shaft 31, an eccentric part 32, a connecting rod 33, and a piston 34. The crank shaft 31 press fits in the rotor 22, to rotate with the rotor 22, and has a lower end submerged in the refrigerating machine oil in the lower shell 11. The eccentric part 32 is provided to an upper end of the crank shaft 31, eccentric from a shaft axis of the crank shaft 31. The connecting rod 33 has one end coupled to the eccentric part 32 on the upper end of the crank shaft 31 with a pin, and the other end coupled to the piston 34 with a pin, for converting rotating motion of the crank shaft 31 into a linear reciprocating motion. The piston 34 compresses the working fluid in a cylinder block 35 with a connecting rod 33.
FIG. 2 illustrates a configuration of connection between the cylinder block 35, the piston 34, the connecting rod 33, and the crank shaft 31, schematically.
When a power is applied to the reciprocating type compressor, the rotor 22 rotates owing to formation of a magnetic field caused by an electric force, and the crank shaft 31 rotates as the rotor 22 rotates. According to this, the connecting rod 33, connected to the eccentric part 32 of the crank shaft 31, swings in left/right directions repeatedly when the drawing is seen from above by a predetermined torque, so that the piston 34 reciprocates in the cylinder block 35 linearly, to draw, compress, and discharge the refrigerant repeatedly, according to valve actions of a suction valve, and a discharge valve.
However, the related art reciprocating type compressor can not, but be involved in over compression due to a generally fast compression rate in compressing the refrigerant. Of course, the rotation speed of the rotor 22 may be reduced for solving the problem, however, when the suction rate of the refrigerant becomes slow, to cause difficulty in drawing the refrigerant. Particularly, even though a greater torque from the electric driving part 20 is required at a top dead center as far as there is no time delay at the top dead center, the greater torque in turn requires a larger electric driving part 20.
Moreover, the compression and re-expansion within a half cycle in the case of the related art reciprocating type compressor causes a great variation of the torque, to require a larger electric driving part 20 in comparison to rated output or affect the suction efficiency.